A conventional and ordinary video display device comprises a display (hereinafter, referred to as “standard color gamut display”) displayable of a video in colors in a color reproduction range conforming to the sRGB (standard RGB) standard, a national standard of IEC (International Electrotechnical Commission). In contrast, a recent video display device, particularly a liquid crystal display device, realizes a higher quality picture, having a wider representable range of colors than the conventional device.
For example, when a video signal conforming to the sRGB standard is input, and when video display is conducted by directly using the video signal, a liquid crystal display device, having; a backlight that has an LED of a high color purity in light emission colors as a light source and, a liquid crystal panel (an example of a display) illuminated by the backlight, displays video in colors in a color reproduction range (hereinafter, referred to as “expanded color reproduction range”) wider than that of the sRGB standard. Such a display (hereinafter, referred to as “wide color gamut display”) is displayable of brighter (higher saturation) colors than the standard color gamut display.
FIG. 2 shows a case when conducting video display based on a video signal conforming to the sRGB standard. The figure shows, on a chromaticity diagram, a color reproduction range CS1 displayed on the standard color gamut display and a color reproduction range CS2 displayed on the wide color gamut display.
In FIG. 2, the positions of three points P1r, P1g, and P1b in the color reproduction range CS1 of the standard color gamut display show red, green, and blue of the highest saturation in the color reproduction range CS1 respectively. Similarly, the positions of three points P2r, P2g, and P2b in the color reproduction range CS2 of the wide color gamut display show red, green, and blue of the highest saturation in the color reproduction range CS2 respectively.
As shown in FIG. 2, the color reproduction range CS2 is broader than the color reproduction range CS1, and the wide color gamut display is therefore displayable of colors having the saturation higher than that of the standard color gamut display.
And also, in FIG. 2, a straight line L1r (an equal hue line of red) is shown with a thick dash line that represents a color range of an equal hue from achromatic colors (position of a point Pw) of the lowest saturation to red (position of a point P1r) of the highest saturation in the standard color reproduction range CS1. Similarly, a straight line L2r (an equal hue line of red) is shown with a thick dash line that represents a color range of an equal hue from achromatic colors (position of a point Pw) of the lowest saturation to red (position of a point P2r) of the highest saturation in the expanded color reproduction range CS2.
Furthermore, FIG. 2 shows solid lines: L0r, L0g, L0b, L0c, L0m, and L0y, for red, green, blue, cyan, magenta, and yellow, respectively that represent a color range of equal hues visually sensed as having the same hue from achromatic colors to each color (chromatic color). In short, the solid lines L0r, L0g, L0b, L0c, L0m, and L0y represent the equal hue lines of each color: red, green, blue, cyan, magenta, and yellow. The visually equal hue lines L0r, L0g, L0b, L0c, L0m, and L0y for each color shown in FIG. 2 are also described in the Nonpatent literature 1.
Here, the red hue is described.
FIG. 3 shows, in close-up, equal hue lines of red L1r and L2r in the standard color reproduction range CS1 and the expanded color reproduction range CS2 respectively and a visually equal hue line of red L0r. 
As shown in FIG. 3, the visually equal hue line of red L0r has a shape curved in a direction having a convexed shape near the yellow hue.
The red equal hue line L1r in the standard color reproduction range CS1 is a straight line, however, closely resembles to the visually equal hue line of red L0r. Therefore, when video display based on a video signal conforming to the sRGB standard is conducted on the standard color gamut display, with respect to reddish video, a signal value of an equal hue is reproduced by colors having approximately the same hue from achromatic colors (position of the point Pw) to a color of the highest saturation (position of the point P1r). However, the color reproduction range CS1 of the standard color gamut display is narrow, and thus, the brightness for displaying red having a high saturation lacks. In addition, for a video signal conforming to the standards other than the sRGB standard (for example, sYCC standard), video display may be conducted by inputting the video signal to a display having the color reproduction range same as that of the standard, so that the red color of equal hue is displayed by a primary color.
Additionally, the red equal hue line L1r in the standard color reproduction range CS1 has red of the highest saturation (the position P2r) that closely resembles to the visual red of a high saturation.
Therefore, when video display based on a video signal conforming to the sRGB standard is conducted on the wide color gamut display, with respect to red having an extremely high saturation, the primary color the video signal indicates is reproduced highly brightly in the video.                Patent literature 1: Japanese Unexamined Patent Publication No. H08-130655        Nonpatent literature 1: G. Wyszecki, and W. S. Stiles, “Color Science: Concepts and Methods, Quantitative Data and Formulae”, 2nd ed., New York, John Wiley & Sons Inc., 2000, p. 447        